With the wide application of Ethernet techniques in a Local Area Network (LAN) and a Metropolitan Area Network (MAN), kinds of network devices are growing and configurations thereof are complex, and users have higher requirements for Ethernet management capacities. At present, an auto discovery function is used in many network management systems to track changes of topology. However, this function can only analyze a topological structure of a network layer. Information, such as which interfaces are provided by a device, which interfaces are connected to other devices, and paths between clients, network devices and respective servers, is obtained by a link layer. The user has to obtain enough detailed information to pinpoint network failures. Meanwhile, a standard information communication platform is needed, so that devices from different operators are able to discover each other in the network and to exchange their system and configuration information. An LLDP function is proposed under such background.
The LLDP is a kind of link layer discovery protocol defined in an Institute of Electrical and Electronic Engineers (IEEE 802.1AB) protocol and provides a standard link Layer discovery manner, through which a device may package information (such as a device identification, a interface identification, a main function, a management address of the device at one end) into various Type/Length/Value (TLV), and sends them to neighbours directly connected with the device by encapsulating them into Link Layer Discovery Protocol Data Unit (LLOPDU); the neighbours stores the received LLOPDU information and display them to users in a Command Line Interface (CLI) manner or in a standard Management Information Base (MIB) form. The network management system may quickly learn topology of layer-2 and changes of the topology through this protocol, so as to query both connection paths between the network management system and neighbour devices in the network and physical information such as device models of these neighbour devices, in order to help the network manager to know the network topology, so that the network manager may perform a network management system query, a network statistics, and diagnosis of link communication state based on the network topology.
Packet Over SONET/SDH (POS) interfaces will be described hereinafter.
A Synchronous Optical Network (SONET) is a synchronous transmission technology defined by an American National Standards Institute (ANSI), and is a standard transport protocol of globalization by using optical transmission.
A Synchronous Digital Hierarchy (SDH) is defined by a International Telephone and Telegraph Consultative Committee (CCITT) (which is also called International Telegraph Union Telecommunication Standardization Sector (ITU-T) at present), and uses a synchronous multiplexing manner and a flexible mapping structure to directly add-drop low-speed branch signals from SDH signals without a plurality of multiple connection/tapping equipments, so that loss of signal and equipment investment may be reduced.
The POS interface is used in both the MAN and the WAN, and has an advantage of supporting packet data, such as IP data packets.
The POS interface directly maps variable-length data packets to SONET synchronous payload, uses physical layer transmission standard of the SONET, and provides a high-speed, reliable and point to point data connection.
The POS interface may use a Point to Point Protocol (PPP), frame relay and a High-Level Data Link Control (HDLC) protocol in the data link layer, and may use an IP protocol in the network layer. Transmission speed of interfaces may be different for different devices, for example, each level of STM-1, STM-4 and STM-16 has 4 times speed of the next lower level.
Physical parameters of the POS interface needs to be configured according to configuration or application of a network device at an opposite end, before configuring the link protocol and the network protocol.
A Universal Logic Ether Interface (ULEI) will be described hereinafter.
The ULEI is a logic interface with Ethernet nature. The ULEI has a physical Ethernet interface attribute, and basically supports all Ethernet services including a sub-interface, a Virtual Local Area Network (VLAN), QINQ, L2VPN, L3VPN, routing, Bidirectional Forwarding Detection (BFD), Multiple Spanning Tree Protocol (MSTP) and the like. The purpose of the ULEI is as follows.
(1) VPN bridging between a second layer and a third layer, i.e., to bridge the second layer VPN to the third layer VPN in one device.
(2) A common logical Ethernet interface designed to implement Ethernet services (such as bridging an ETH service including extended supported FR, ATM) via a non-Ethernet interface; the ULEI is used to shield differences among a plurality of different interfaces so that physical interfaces cannot be felt during service process.
Additionally, a bridging ULEI must be provided on an ETH interface board; a heterogeneous ULEI must be provided on a POS interface plate; ULEIs having a binding bridging relationship must be provided on a same line card.
The LLDP only defines achievement of the LLDP function on the Ethernet, and a conventional protocol standard does not relate to how to enable the LLDP function on a non-Ethernet link WAN such as a POS interface, and does not regularly define that interfaces such as the POS interface are able to support an LLDP neighbour discovery function.